Impact-operable electric alarm switch devices



June 5, 1962 Filed July 13, 1959 H. s. HALL ETAL 3,038,042

IMPACT-OPERABLE ELECTRIC ALARM SWITCH DEVICES 3 Sheets-Sheeti Inventors H 5. H A LL M IEVERITT June 5, 1962 s. HALL ETAL 8,

IMPACT-OPERABLE ELECTRIC ALARM SWITCH DEVICES Filed July 13, 1959 3 Sheets-Sheet 2 0 3 2 L 9 A kZ////////////// 6 w a 3 w Z 0 03 //////r/// J N My w MB 3 mLW wLR 1.. EM SI W HM June 5, 1962 s. HALL ETAL 3,033,042

IMPACT-OPERABLE ELECTRIC ALARM SWITCH DEVICES Filed July 13, 1959 5 Sheets-$heet 3 l'mgentors H S. HALL M IEVERH'T 24W wM+ M A ttorneys United States Patent 3,038,042 IMPACT-OPERABLE ELECTRIC ALARM SWITCH DEVICES Harvey S. Hall and Michael J. Everitt, Cambridge, England, assignors to Cathodeon Limited, Cambridge, England, a British company Filed July 13, 1959, Ser. No. 826,747 Claims priority, application Great Britain July 15, 1958 3 Claims. (Cl. 20061.08)

The present invention relates to impact-operable electric alarm switch devices for completing electrical circuits in the event of emergencies, for example for fitting to vehicles, including aircraft, whereby in the event of collision or crashing the impact will cause the switch to operate, for example to actuate an audible or visible alarm signal device or a control device to disseminate fire-extinguishing media.

A switch device for this purpose is known, that comprises an outer casing of frangible material having an elongated tubular form closed at one end, a rod'electrode enclosed within said outer casing and extending substantially coaxially of the casing and for substantially the entire length thereof, and a coiled electrode surrounding and spaced from the rod, the two electrodes being adapted to be connected to a suitable electric circuit, and the arrangement being such that the said circuit is completed upon fracture of the outer casing due to an impact. Moreover, there is also known a switch device of this kind in which the end of the rod electrode at the closed end of the outer casing is located in a block of insulating material to prevent lateral movement of the rod in the inoperative state of the switch.

It is an object of the persent invention to effect improvements in or modifications of these arrangements whereby a double-pole switch device is provided so that various circuits may be controlled by each switch.

According to the present invention there is provided an impact-operable electric alarm switch device comprising an outer casing of frangible material having an elongated tubular form closed at one end, two or more pairs of rod electrodes enclosed within said outer casing and extending substantially coaxially thereof, a member of insulating material also mounted coaxially of said casing and between said electrodes and means for moving said member of insulating material in the event of an impact damaging the switch device so as to connect selected pairs of said electrodes together electrically.

The switch device of the present invention is applicable for many purposes: for example in aircraft one set of contacts comprising one pair of rod electrodes may be connected to a control means for disseminating fire-extinguishing fluid, and another switch comprising another pair of rod electrodes may be connected to light an alarm lamp in the view of the pilot, or to sound an audible alarm or both.

Two switches may be mounted in a given circuit so that both of them must operate before the circuit is energised; The second pair of contacts in each switch would then be connected to individual indicator lamps or other warning devices so that the pilot may have an indication if one of the switches should break under circumstances other than a crash condition.

The construction of switch devices according to the present invention allows this facility more conveniently than with the devices according to the two prior patents referred to.

In order that the invention may be more clearly understood reference. will now be made to the accompanying drawings which illustrate two specific embodiments thereof by way of example and in which:

FIGURE 1 shows a section through one embodiment,

FIGURE 2 shows a section through a second embodiment,

FIGURE 3 shows a side view of the switch of FIGURE 2 but rotated through FIGURE'4 shows a section of a part detail along the line B--B of FIGURE 3, and

FIGURES shows an axial-section through a third em bodiment.

Referring to FIGURE 1, there is shown a frangible envelope'l, which may be made from glass, a mounting flange 2 of metal for securing the device to the vehicle and a base seal 3. The envelope 1 and the seal 3 are hermetically sealed together. The flange 2 may be soldered to the seal 3 or may be hermetically sealed to the envelope and the seal. A pillar 4 is mounted on the centre of the base seal 3 and to the head of this pillar there is bolte d a block 5 of insulating material by means of a nut 6 and lock nut 7 which are secured to a threaded extension 8' of the pillar which extension passes through an "aperture in the block 5. Four or more switch contact rods 9, two of which are visible in the drawing are mounted in seals 10 in the base seal 3 and these extend to locate in apertures 11 in the block 5. The contact rods 9 are housed in contactor eyelets 12 which'have a contact surface 13 on the face of the insulator block 5. The contact rods 9 are connected by wires 14 to terminal units 15 which are spaced around a block 16 of insulating material, which may for example be of a synthetic resin, the said block 16 being moulded around the complete assembly as shown. Apertures 17 are provided in the mounting flange 2 to enable the synthetic resin to be moulded above and below the flange as one piece, thereby improving the appearance.

The moving contact member for theswitch comprises a pillar or piston 18 of insulating material having longitudinal apertures 19 and 20 extending therethrough for the passage of the contact rods 9 and the pillar 4 respectively whereby the pillar or piston 18 is free to slide longitudinally along the-said rods and pillar 4. A make spring 21 is located between a flange orshoulder 22 on the piston or pillar 18 and the base seal 3 so as to urge the piston 18 towards the insulator block 5 and a hold off spring 23 is located between a further shoulder 24- on the piston 18 and the frangible envelope 1: this hold off spring is sufficiently powerful to overcome the thrust of the makefspring 21 and hold the piston 18 down in contact with the base seal 3 whilst the envelope 1 is intact. If desireda centering block 25 may be provided to keep the spring 23 in place, the said spring resting on a shoulder 26 of theblock 25: the block 25 may be made from an insulating material.

On the free face 27 of the piston 18 there are provided fixed contactor plates 28 which areshaped as desired to make the desired connection between the various conductor eyelets 12 when the piston 18 is forced down by the make spring 21 in the event of the envelope 1 being smashed.

If desired, however, the piston 18 may have only a central aperture for the pillar 4 and its outside diameter may fit just inside the-contact rods 9. In this case the fixed contact plates, which would be located around the outer diameter of the piston 18, might be adequate for ensuring electrical contact but a face plate of metal suitably drilled out to the shapes required could be added if necessary. The hold off spring 23 could then engage ex-' tending pins or this metal plate. If the fixed contact plates are judiciously proportioned and located it would be possible to provide for connection being made directly to the contact rods in the event of the applied breaking 0 force not only smashing the envelope 1 but forcing the fixed insulator block 5 off centre.

Referring now to FIGURES 2 and 3 there is shown an;

embodiment which is more versatile than that shown in FIGURE 1 because this switch may act whatever directional force be applied. It will act if the spring urges the insulator away from the base seal or if the insulator is forced against the base by external pressure as well as if the insulator is wrenched sideways.

The basic assembly is similar to that of FIGURE 1 in so far as the frangible envelope 29 and the base 30 are concerned but the operating mechanism is modified. The contact rods 31 extend from the base seal 32 but they are free at their opposite ends 33. On each rod there is mounted a contact leaf spring34 which extends around the opposite contact rod of the pair and has silver contact 35 positioned to provide the connection in the event of the switch being operated. As shown in the section of FIGURE 4, which is given to show a leaf spring in the open position, each leaf spring is continued in an arcuate or L=shape around the other contact rod to ensure connection if the switch is subjected to a sideways wrenching force, which leaf spring is tensioned to provide adequate contact pressure against the other contact rod of the pair. Because each rod 31 has its own leaf spring as clearly shown in the drawings, this menas that all the connections are duplicated so as to ensure reliable operation.

In this embodiment the piston 36 of insulating material is provided with a plurality of external ribs 37 and is free to slide longitudinally of the switch between the pairs of contact rods 31. A spring 38 is located between the piston 36 and the base seal to hold the piston 36 firmly against the frangible envelope, the head 39 of the piston 36 being shaped as shown so as to contact the inner wall of the envelope 29. The ribs 37 lie opposite the contact leaf springs 34 when the switch is assembled and the diameter of these ribs is sufiicient to hold the springs away from the other contact rods of the respective pairs. However, a slight movement of the piston 36 in either longitudinal direction will bring the narrower diameter of the piston 36 between the ribs 37 opposite the leaf springs and they are therefore free to spring into contact with their opposite contact rods of the pairs. Moreover should the piston 36 be wrenched sideways in any direction then, for example in a four contact rod arrangement as shown in FIGURES 2 and 3, at least two leaf springs 34 will be free to act normally while the other one or two springs will make contact with the rods which have been bent or deformed.

The contact rods are hermetically sealed within the glass envelope to avoid deterioration of the contact surfaces and these can be further protected by evacuating the envelope or filling it with a suitable gas such as nitrogen, hydrogen or argon.

The head 39 of the piston 36 may be provided with a soft iron slug 40 which renders it possible to test-actuate the switch by means of a suitable solenoid, or permanent magnet if desired without fracturing the envelope 29. This slug may be secured to the piston head 39 in any convenient fashion, for example by a pin (not shown) passing through the slug and piston head.

If it is desired to make the arrangement flame-proof several precautions must be taken. It is not possible in such an event to connect the seals in a normal manner, for example by soldering or even welding as this would not be reliable enough for extreme operating conditions but the metal plates must be secured together by other mechanical means, for example bolts. The base block 16 or 30 must be made of a material which is able to withstand the extremes of temperature called for and as may be met in dangerous positions on the vehicle.

The switch of FIGURE is a modification of the arrangement shown in FIGURES 2, 3 and 4 and therefore like reference numerals in the two arrangements refer to like parts. Principally, the base 30 of the arrangements of FIGURES 2, 3 and 4, which is made from an organic plastic material, is replaced by a mild steel housing which also incorporates the mounting flange and its end opposite to the frangible envelope 29 is fitted with a standard multi-pin connector. The arrangement of this modification enables the switch to be more resistant to higher temperatures and to provide facilities for connecting to standard connectors.

In FIGURE 5 the base seal 32, upon which is secured an organic plastic support 41 for example of po'lytetrafluoroethylene, with a spring 38 as in the arrangements for FIGURES 2, 3 and 4, is supported in the termination 43 which is in the form of a housing of mild steel integral with a flange 44 for mounting the switch. The casing is filled with an insulating material 45 which is preferably a silicone elastomer and at its free end the housing is secured, eg by screws to a standard multi-pin connector 46 which is externally screw-threaded at 47 to be received into a standard socket. Since this multi-pin con nector 46 may take any well-known form and per se forms no part of the invention, it will not further be described here, but in general it may contain two pairs of pins connected by the cables 48 respectively to the contact pairs 35, together with one or more dummy or locating or earth pins.

Between the base seal 32 and a shroud 49 depending from the flange 44, there may be provided spring washers and split washers and a turnover flange secured to the envelope 29, as shown, so as to secure the envelop 29 in position in relation to the housing 43 with its shroud 49 in accordance with conventional practice. A thimble 50 is screwed into the shroud 49 to clamp up the envelope in position but the interposed spring and split washers impart a resilience to this clamping so as not to damage the suspension of the envelope.

The slug 40 of soft iron may be secured to the head 39 of the piston 36 by means of a pin 42 which passes through the slug and the piston head and which may be of nickel plated metal.

The operation of the switch according to FIGURE 5 is the same as that described in the embodiment of FIG- URES 2, 3 and 4.

We claim:

1. An impact-operable electric alarm switch device comprising an outer casing of frangible material having an elongated tubular form closed at one end, a mounting flange of metal, a base seal connected to said flange and hermetically sealed to said frangible casing, a pillar of insulating material mounted for longitudinal movement within said casing, spring means between said piston and said base seal, a plurality of pairs of rod electrodes passing through said base seal and located in spaced relation around said piston, a contact leaf spring mounted on each of said electrodes so as to extend around the next adjacent rod electrode towards its cooperating rod electrode of a pair, a contact member at the end of each of said leaf springs to make contact with said cooperating rod electrode of a pair, a plurality of external ribs on said piston, said rod electrodes riding on said ribs, and a head at the free end of said piston, said head being shaped so as to hold said piston firmly against the frangible casing in the inoperative condition of said switch.

2. An impact-operable electric alarm switch device comprising an outer casing of frangible material having an elongated tubular form closed at one end, a mounting flange of metal, a base seal connected to said flange and hermetically sealed to said frangible casing, a pillar of insulating material mounted for longitudinal movement within said casing, spring means between said piston and said base seal, a plurality of pairs of rod electrodes passing through said base seal and located in spaced relation around said piston, a contact leaf spring mounted on each of said electrodes so as to extend around the next adjacent rod electrode towards its cooperating rod electrode of a pair, a contact member at the end of each of said leaf springs to make contact with said cooperating rod electrode of a pair, a plurality of external ribs on said piston, said rod electrodes riding on said ribs, a head at the free end of said piston, said head being shaped so as to hold said piston firmly against the frangible casing in the inoperative condiiton of said switch, and said head being recessed to receive a slug of ferromagnetic material, and means securing said slug to said piston head.

3. An impact-operable electric alarm switch device, comprising an outer casing of frangible material, at least two pairs of rod electrodes fixed within said outer casing and extending substantially co-axially thereof, an electrical contact spring secured to each. of said rod electrodes, at contact member mounted on said contact spring, a piston of insulating material located to move longitudinally within said casing, means for moving said piston upon fracture of said frangible casing, and means on said piston normally spacing said contact member away from another of said rod electrodes, movement of said piston on breaking of said casing moving said piston to allow said contact member to contact said other rod electrode.

References Cited in the file of this patent UNITED STATES PATENTS 1,223,866 Graham et al Apr. 24, 1917 2,352,692 Dann July 4, 1944 2,783,320 Fink Feb. 26, 1957 

